Appraisal

Rubies (along with other colored gemstones) are assessed primarily by their hue. The most expensive rubies have a rich and vivid red color. Clarity and cut are also important factors in their appraisal.

Treatment

In the book "The Heat Treatment of Ruby and Sapphire," heat treatment is described as a process that enhances the clarity and color of the stone. Although heat is used in almost all commercial stones, natural rubies that are untreated (or treated at low temperatures) fetch higher prices.

Varieties

According to "Ruby & Sapphire," Burmese rubies are the most popular worldwide and, consequently, fetch the highest prices on the market. Other natural sources are found in Tanzania, Thailand and Afghanistan.

Value

A ruby of fair quality from the above sources can start at about $400 per carat, and one of exceptional quality can run as high as $4,600 per carat.

Demand

According to a Feb. 16, 2006, article on Bloomberg.com, demand for precious stones are increasing. Laurence Graff, a London jeweler, paid a record $425,000 per carat for a ruby ring. He paid $3.6 million for the 8.62-carat stone at a Christie's International auction.

Source:

"The Heat Treatment of Ruby and Sapphire;" Ted Themelis; 1992

"Ruby and Sapphire;" Richard W. Hughes; 1997

Bloomberg.com: Christie's Sells Ruby to London Jeweler Graff for $3.6 Million

More Information:

Multicoulor.com: Natural Ruby